NASA sniffs out (yet more) lunar ice

NASA has announced that the Moon's north pole is packing substantial amounts of water ice, lurking in around 40 small craters.

The evidence comes from the agency's Mini-SAR (aka Mini-RF) instrument, a synthetic aperture radar which travelled aboard India's Chandrayaan-1 spacecraft. The device used "the polarization properties of reflected radio waves to characterize surface properties", and determined that deposits in permanently-shadowed craters at the pole have characteristics "similar to ice".

The craters range from 2 to 15 km in diameter, and while the total amount of frozen water depends on the deposit thickness in each, NASA has calculated it as "at least" 600 million metric tons.

Paul Spudis, Mini-SAR principal investigator at the Lunar and Planetary Institute in Houston, said: "The emerging picture from the multiple measurements and resulting data of the instruments on lunar missions indicates that water creation, migration, deposition and retention are occurring on the moon.

"The new discoveries show the moon is an even more interesting and attractive scientific, exploration and operational destination than people had previously thought."

NASA's latest findings - published in the journal Geophysical Research Letters - add to a solid body of evidence for lunar ice. In September last year, other results from the Moon Mineralogy Mapper (M3) on Chandrayaan-1, and NASA's Cassini and Deep Impact missions provided "unambiguous evidence for the presence of hydroxyl* or water" on the Moon.

The Lunar CRater Observation and Sensing Satellite (LCROSS) then showed there was plenty of ice at the Moon's south pole.

While it's evident that future Moon explorers will have no shortage of cold stuff to stick in their gin and tonics, one question remains: where did the Moon's water come from? It's possible that it arrived on water-bearing comets which impacted on the surface or, according to NASA's M3 team, by way of an "endogenic" process.

The M3 scientists have suggested that if the solar wind's positively-charged hydrogen atoms impact against the Moon's surface with sufficient force they can "break apart oxygen bonds in soil materials", and "where free oxygen and hydrogen exist, there is a high chance that trace amounts of water will form".